fix(shared): drop .js extensions from relative imports for Metro

packages/shared/src/index.ts and all sub-modules used .js extensions on
relative imports (e.g. './admin/index.js') pointing at .ts source files.
TypeScript with moduleResolution: "Bundler" doesn't need them, and
Metro's eager exporter (used for preview / production builds) reads
them literally and fails — only the dev-server Metro fell back to .ts.

Workspace typecheck remains 8/8 green; Vite and TS Bundler resolution
already accept both styles, so desktop is unaffected.

packages/shared/src/admin/index.ts

@@ -1,8 +1,8 @@
-// Admin-only helpers. Every call is RLS-gated server-side via the
+// Admin-only helpers. Every call is RLS-gated server-side via the
 // `current_user_is_admin()` helper + admin-specific policies. Non-admins
 // trying to call these still get clean PostgREST 403/empty-result responses.
 
-import type { AppSupabaseClient } from '../supabase/client.js';
+import type { AppSupabaseClient } from '../supabase/client';
 
 // --- Admin settings -------------------------------------------------------
 
@@ -189,7 +189,7 @@ export async function setUserFlag(
 }
 
 // ---------------------------------------------------------------------------
-// Conversations (admin view — reads all regardless of membership)
+// Conversations (admin view — reads all regardless of membership)
 // ---------------------------------------------------------------------------
 
 export interface AdminConversationRow {